Telephonic instrument, including transmitters.



W. P. STUNZ.

TELEPEONIC INSTRUMENT INCLUDING TRANSMITTERS.

FILED APR.13,1911.

APPLICATION Patented June 25, 1912.

WJZT-JESSES n v 1 H A bran. s'rar FlCE.

WILLIAM PRESTON STUNZ, OF LANSDOWNE, MARYLAND, ASSIGNOR TO GEORGE REGESTER 'WEBB, OF BALTIMORE, MARYLAND.

TELEPHONIC INSTRUMENT, INCLUDING TRANSMITTERS.

Specification of Letters Patent.

Patented J one 25, 1912.

Application filed April 13, 1911. Serial No. 620,960.

To all whom it may concern: 1

Be it known that I, l Vimimir Pnns'roN Sirens, a citizen of the United States rosiding at Lansdowne, in the county of Baltimore and State of Maryland, have invented certain new and useful lmprov'ements in Telephonic instruments, Including Trans n'iitters; and I do declare the hillowing to be a full, clear, and exact description of the invention, such as will enable others skilled in the artto which it appertains to malre and use the same, reference beiu ha d to the accompanying drawings, and to the letters and figures of reference marked thereon, which form a part of this specification.

My invention relates to telephonic instruments, more particularly to microphone or granular carbon transmitters.

Each grain or granule of carbon in telephone instruments constitutes a resistance unit and when the granules are subjected to an excess or overcharge of current heat is generated and when the granules thus bccome over-heated their resistance capacity is proportionately lowered. Accordingly the current carrying" capacityiof the granular carbon is limited or diminshed relatively as the degree of resistance is lowered occasioned by the overheating of the carbon. It follows that if this overheating of the carbon granules is prevented the maximum current carrying capacity of the carbon granules obtained, and to the extend-that the c: rbon granules are rendered capable of carrying a heavier current to that cxtentthe load to be carrie-al on the line canbe increased and a "all of voltage due to lowering theresistance ot the carbon granules is overcome and this results in making it possible to employ a greater number of instruments on the line.

lily invention accordingly has primarily for its object to maintain a normal or low condition of temperature in the carbon granules under conditions in which other wise the current-would ovcr-hcat the carbon granules and lower their resistance and this l ellect by the application of a cooling agent, to act upon the carbon granules so as to keep down their temperature and thus preventtheir ovcnhcating and consequent lowering of their resistance-and by such means malt-- ing it possible to carry a heavier current on the line.

To the accomplishment of the foregoing I have selected for the purposes of illustration a multiplex microphone or granular carbon transmitter having embodied therein one form of the invention but, withoutu'ieaning however to restrict the invention to such particular form or to such particular use except as may be specified as it is the purpose to cover the invention comprehensively in whatever form or to whatever kind of instrument employinggranular carbon as the resistance it may be used.

In the accompanying drawings illustrating one-form of theinven ion: Figure 1 rep-resents a front elevation of several indi vidual transmitters constituting a multiplex transmitter; Fig. 2 is a vertical section through two of the individual transmitters and having my invention applied thereto; Fig: 3 is a partially vertical sectional view through the cooling chamber, on a larger scale than the other views; .and Fig. 4 is an end view of the cooling chamber with its face or electrode omitted.

In Fig. 1. of the dawing there is illus trated a multiplex transn'iitter of the form shown in U. q. Patent No. 943,115 granted Dec. 21, 1909 to George R. N ebb, as assignce, and in which the movable electrodes of the individual transmitters are connected to the branch arms of an oscillatingr member 1 so that when said member oscillates in one direction the granular carbon in two of the initlividual transmitters is compressed and the carbon in the other two transmitters permitted to loosen up, and in the oscillating of the member in the other direction the granular carbon in the trans mittcrs previously loosened up is compressed while that in the other transmitters is loosened up, and in which alsois shown acircuit in which two of the movable electrodes are legged to a branch wira E2 of the line, and the movable electrodes of the other two individual t-rausn'iitters legged to a branch wire 3 of the? line while the immovable electrode of one indii-idual transmitter is connra-tcd by wire 4 with the immovable electrode of one of the other individual transmitters, as illustrated, said wire being also connected with one pole of a battery or other 10-5 source ot electrical energy. The other two individual transmitters are connected by a wire 5' leading from their rear or immovable electrodes which wire also leads to the other pole of the battery or source of electrical merely energy. This particular form of multiples: {be connected by a rubber or insulating tubtransmitter however, and the circuit described, indicates merely one form of trans mitter and circuit in which my present invention may be employed and is given an illustration of one form in which the invention may be employed without limiting the invention to such form. .In.

Fig. 2 of the drawing is ilh'lstrated a vertical'sect-ion through two individual transmitters such as shown in Fig. 1 of the drawing but having applied thereto the present invention in one t'orrn, and, so far as I have knowledge at present, the best or preferred form for its application.

The present invention consists in providing means for preventing the over-heating or" the carbon granules 1n the working of the device so that their maximum eihciency is maintained and a heavier electrical current may be employed so that the load to be carried on the line may be increased.

One form or embodiment of time invention is illustrated in Fig. 2 of the drawing 1n which the numeral '6 designates the cup for holding the granular carbon 7 and formed of felt or other suitable material while 8 1ndicatcs a movable electrode and 9 a fixed or stationary electrode. This fixed electrode is carried by a shell or hollow'cup 10 of suitable material and may have ,the fixed electrode secured thereto by overlapping the edges of the cup on to the edges of the elec trode This shell or cup forms a hollow chamber adapted to receive a suitable co0ling agent, which for illustration may be water although any other suitable cooling fluid or agent may be employed. The cooling agent in this shell or chamber contacts with one face of the tired electrode and its cooling influence is transmitted through the electrode to the granular carbon so that the temperature of the granular carbon is keptcomparatively low under various charges of current, and this cooling of the granular carbon prevents lowering its resistance properties which ordinarily isreduced or diminished under an'excess or over-charge'of current and to the extent to which such resistance'has been reduced by over-heating impairing the 'eliiciency of the resistance properties of the carbon granules. By cooling the carbon granules it is also made pos sible to employ a heavier current so that. the load to be carried on the line may be correspondingly increased and thus making it possible to employ a greater number ot instruments on the line having the maximum of efficiency. The cooling agent may be supplied from any suitable source to the cooling chamber 10 through a pipe or tube 11, which in practice 'willbe connected with the supply pipe by a rubber or other insulating tubing, and will be discharged from the chamber through pipe or tube 12, which likewise will ing with a discharg conduit. Both the supply and discharge pi es, for controlling or regulating the flowof the coolingagent to pursue a circuitous course in flowing through the chamber and thus attain better results. the interior of the chamber may be provided with a series of partitions 13 which are illustrated as extending cross-wise of the chamber and terminating at one edge short or back of the walls or the chamber so as to form a zigzag or circuitouspassageway for; the flow or passage of the cooling agent. The shell or cup constituting the cooling chamber is provided with a threaded stem 14 by which the chamber and associated parts i may be supported from a suitable support 15. The opening in thes'upport-through which passes thestem may be provided with suitable insulating material 16 and to each side of the support may be placed insulating strips 17, and a nut 18 may be applied to the threaded stem so as to secure the parts together. These features however are matters of more detail and may be varied at will without departing from the essential features of the invention.

While I have illustrated the invention as. applied to a microphone or granular carbon transmitter, and have selected merely for purposes of illustration a multiplex transmitter of the form previously mentioned, yet it is to be understood that the invention is not in all its forms and uses confined or limited to the particular mode of itsapplication illustrated, as the invention in its broadest scope contemplates a constructioh by which a cooling medium is circulated through a chamber separated by an eledtrode from a body of granular carbon so that by the continuous discharge and replacement of the cooling-medium the ma2rimum of resistance in the granular carbon is maintained by preventing the over-heating" of granular carbon in instruments where such material is employed so as to obtain the maximum efiiciency of the granular carbon so far as its resistance properties are concerned and so as to make it possible to employ a heavier current than otherwise without lowering the resistance properties by the current employed. This as previously stated also makes it possible to employ a heavier current so that the load to be carried on the line may be increased and a larger number of instruments employed without impairment In their maximum efficiency. Accordingly it will be understood that while-the invention may be employed in the typeof instruments illustrated and referred to with excellent results yet the invention contemplates its employment Wherever it is desirable to preventthe lowering of the resistance properties of the carbon by over-heating or an excess of electrical current.

Having described my invention and sch forth its merits hat I claim is:

1. In an instrument employing granular carbon as a resistance, the combination With the granular carbon, of a cooling chamber, and means forming a circuitous passageway Within the chamber.

2. instrument employing granular &

carbon as a resistance, com rising a carbon retaining chamber,- electro des on opposite sides of the carbon, a cooling chamber'at one face of one of'the electrodes, a circuitous passageway within said chamber and means for supplying and Withdrawing a cooling agent from said chamber.

In testimony whereof I aiiix my signature in presence of two Witnesses.

WILLIAM PRESTQN STUNZ.

Witnesses:

J. Hoornn EDMONDSON HENRY WV. WEBB. 

